27.9% of all deaths in Korea in 2015 resulted from cancer and the number thereof was 76,855. Cancer deaths are rising steadily every year. Lung cancer was the leading cause of cancer death in Korea and its rate was 17,399 in 2015. The rates of liver cancer, gastric cancer, and pancreatic cancer in both Korean men and women increase in this order. Most of these cancer patients do not die of their primary tumors but of metastases of a broad range of multiple tumor colonies formed by malignant cells that are separated from initial tumors and often migrate to distal sites through blood. Primary tumors detected in the initial stage can be removed by surgery, radiotherapy or chemotherapy but cancer cells circulating in the bloodstream are present at very low concentrations that are difficult to detect. For this reason, the likelihood of success of initial detection of cancer cells in blood is substantially low. Cancer cells in blood refer collectively to cancer cells present in the peripheral blood of cancer patients and are defined as cancer cells that fall off from primary or metastatic lesions. In recent years, approaches have been developed to use cancer cells in blood as potent biomarkers for cancer diagnosis, analysis of therapeutic prognosis, and analysis of micrometastasis. As described above, a very low concentration of cancer cells is distributed in blood. For example, one cancer cell is present per billion normal cells or one to ten million leukocytes in blood. Cancer cells are difficult to accurately analyze due to the presence of interfering factors such as contaminants and air bubbles during analysis. In addition, systems for separating cancer cells from blood are still relatively expensive given that the number of cancer patients is rapidly increasing every year. Most of such systems are disposable and are discarded after use. In addition to this economic burden, the systems are complicated to install.
Specifically, a method for separating cancer cells from blood involves three steps, i.e. blood sample production, sample injection, and cancer cell separation. The blood sample is prepared by mixing and binding blood, an antibody reacting specifically with cancer cells, and a functional material for downstream cancer cell separation such as a magnetic material. Then, the blood sample is injected into a system for cancer cell separation. It is important to inject an accurate amount of the blood sample at a constant flow rate while precluding the entrance of interfering factors, such as contaminants and air bubbles. The magnetic material previously bound to the blood is used as a carrier for cancer cell separation. The system usually includes a plurality of divided flow channels for cancer cells and non-cancer cells. It is important to secure accurate separation of cancer cells by maintaining the flow rates of the substances flowing through the flow channels at constant levels.
Many technologies for cancer cell separation have been investigated so far. Patent Document 1 relates to a method and reagent for rapidly and effectively separating circulating cancer cells and proposes a technique for separating cancer cells from a mixture of blood collected from a patent and a ligand (the can be detected due to its specific reaction with cancer cells). However, this patent document fails to consider the problems of contamination during injection of the blood sample and inaccurate separation of cancer cells. Patent Document 2 proposes a technique for separating cancer cells using ferromagnetic wires. However, this patent document fails to consider technical details for securing preset values for flow channels during discharge and the same amount and rate of substances flowing through the flow channels. Particularly, channels are usually used to accommodate separated cancer cells in a given container. At this time, the flow rate of the cancer cells in each flow channel may vary depending on the length and height of the channel, causing poor separation accuracy.